It is frequently necessary in a strip-treatment plant to join or splice a trailing end of a leading metal strip to the leading end of a trailing metal strip. To do this, the trailing end of a leading strip and the leading end of the trailing strip are positioned one above the other to form an overlap and then are joined together at several points at the overlap by clinching without severing the strip and consequently without any cutting.
In a strip-treatment plant or strip process line, strips rolled up into bundles (coils) are usually unwound at the intake, then run through one or more treatment stations and optionally coiled up again at the output or, as an alternative, are cut into sheets. To avoid having to always rethread the strips, the leading end of a new bundle is joined to the trailing end of the strip of the last bundle. The strip joint is particularly important because defective strip joints can have a negative effect on further processing.
A wide variety of methods for joining strips are therefore known in practice, such a welding, punching and/or adhesive bonding (see EP 2,202,025 [U.S. Pat. No. 8,109,428] and EP 1,749,590 [2007/0029039], for example).
In practice, it has been found that strip joints can also be produced by clinching as an alternative to the traditional method, also known as clinching. Clinching is a method of joining metal strips and/or sheet metal without the use of an additional tool. A clinching tool usually consists of one or more punches and dies. The strips to be joined are pressed by the punch into and/or against the die, as is done in deep drawing with plastic deformation. The strips are joined to one another in a form-fitting (and force-locking) manner without the use of rivets. Due to the design of the dies and punches, the materials undergo a flow in width in and/or on the die, so that a form-fitting connection is implemented—much as in the case of a rivet connection—but without using separate rivets. Clinching within the context of the present invention denotes a type of joining without severing and consequently without cutting.
Such a method of the above-described type is known from WO 2014/033037 [US 2015/0121678], where the joining points are created by clinching as part of the strip-joining process, with an array of joining points extending transversely to the strip-travel direction, forming one or more rows of joining points. It is advantageous if the tool(s) is (are) positioned in a controlled manner.
The known method of joining strips by clinching without severing the strip has proven successful in practice but it could be refined. This is where the present invention begins.